A vortex pump is usually employed for pumping liquids containing a substantial amount of foreign matter such as solids and/or fibriform substances. This kind of foreign matter causes clogging of pumps under operation. Therefore, in the pumps of prior art, an impeller is generally housed within a pocket or a recessed impeller chamber and a vortex chamber is arranged to be generally free of the rotating elements, i.e. the impeller.
However, such pumps of prior art are not satisfactory with respect to the pump efficiency and easiness of releasing air from the impeller chamber, etc. If it is intended to solve these drawbacks by extending the impeller to the vortex chamber, there would be the problem of blocking or clogging of the pump.